DUNEDIN, Fla. - Sean O'Sullivan arrived at the Phillies' minor-league complex before sunrise Tuesday. The 27-year-old righthander did not know that in a little more than five hours he would start a 10-6 loss to the Blue Jays.

"My wife was looking online and she said, 'Hey I think you're starting for the Phillies tomorrow,' " O'Sullivan said. "And I was like, 'I'm not going to believe anything until someone tells me what's happening.' "

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O'Sullivan, a potential temporary No. 5 starter, allowed four runs on five hits and was removed in the fifth inning after a leadoff home run. The Phillies could avoid using a fifth starter until April 12 and will likely need to fill only two or three starts until Chad Billingsley is ready.

Righthander Kevin Slowey, once viewed as a candidate to be the fifth starter or long reliever, was released Tuesday.

"To be down in minor-league camp for the last couple weeks and still have a chance to fight for the spot is unorthodox," O'Sullivan said. "[You] try to put those things as far back in your mind as you can."

Billingsley, coming off consecutive seasons lost to elbow surgeries, will start his third minor-league game Thursday. The 30-year-old righthander is slated to throw 40 to 45 pitches. After the Phillies break camp that evening, he will stay in Clearwater to make likely two or three starts in extended spring training before joining the major-league rotation.

Pettibone eyes May

Twenty-two pitches to the Phillies' back-up catcher and a pair of non-roster invitees marked progress for Jonathan Pettibone. The 24-year-old righthander threw live batting practice at the team complex in Clearwater, the first time he opposed hitters since shoulder surgery in June.

Sometime in May, Pettibone said, is a realistic goal for when he should be ready to rejoin a rotation. He would likely start in triple A with a chance to work his way back to the majors.

Two more live batting practice sessions await. The next step is to pitch in extended-spring training games to build his pitch count and innings. That should begin in a couple of weeks and could take a month.

"Anytime you're facing a live hitter and you have the adrenaline going and you've got to mix your pitches, that kind of competitive edge comes out," said Pettibone, who threw to Cameron Rupp, Brian Bogusevic, and Rene Garcia. "When you're able to get through that and succeed and you felt good, that's definitely a positive step going forward."

- Matt Breen and Jake Kaplan